1. Field of the Invention
The present invention relates to an outboard engine system in which a passage defining member having a passage wall defining an exhaust gas passage for guiding an exhaust gas from an engine is provided at an outer wall thereof with a recess and a seal surface surrounding the recess; a fluid passage isolated from the exhaust gas passage is defined between the recess and a lid member which is mounted to the outer wall of the passage defining member with a seal member interposed between the lid member and the seal surface; and an exhaust gas sampling pipe is inserted into the exhaust gas passage through an insertion bore which is provided in the passage defining member to open into the seal surface. The invention particularly relates to an improvement of a structure of mounting of the exhaust gas sampling pipe.
2. Description of the Related Art
Such an outboard engine system is conventionally known from Japanese Patent Application Laid-open No.6-144374, for example.
In the above conventionally known system, a cylinder block as the passage defining member is provided with a recess for defining a water jacket which is the fluid passage isolated from the exhaust gas passage by the passage wall. The recess is covered with the lid member, and the exhaust gas sampling pipe inserted into the exhaust gas passage is screwed into the insertion bore which opens into the seal surface. The lid member is provided with an opening for disposition of the exhaust gas sampling pipe.
With such conventionally known structure, the size of the opening provided in the lid member must be set at a large value to ensure that the interference with the exhaust gas sampling pipe can be avoided. As a result, the size of the lid member is correspondingly increased, and there is a possibility that the position of mounting of the lid member in the passage defining member may be limited.
The present invention has been accomplished with such circumstances in view, and it is an object of the present invention to provide a structure of mounting of an exhaust gas sampling pipe in an outboard engine system, wherein the exhaust gas sampling pipe can be inserted into the exhaust gas passage, while avoiding an increase in size of the lid member.
To achieve the above object, according to the present invention, there is provided a structure of mounting of an exhaust gas sampling pipe in an outboard engine system in which a passage defining member having a passage wall defining an exhaust gas passage for guiding an exhaust gas from an engine is provided at an outer wall thereof with a recess and a seal surface surrounding the recess; a fluid passage isolated from the exhaust gas passage is defined between the recess and a lid member which is mounted to the outer wall of the passage defining member with a seal member interposed between the lid member and the seal surface; and an exhaust gas sampling pipe is inserted into the exhaust gas passage through an insertion bore which is provided in the passage defining member to open into the seal surface, wherein the seal member is formed to surround an opening at an outer end of the insertion bore, and the exhaust gas sampling pipe is passed through and gas-tightly fixed in the lid member.
With such arrangement, the exhaust gas sampling pipe is gas-tightly fixed in the lid member to extend through the lid member. Therefore, the lid member may have a space enough to allow the exhaust gas sampling pipe to pass through the lid member, and the exhaust gas sampling pipe can be inserted into the exhaust gas passage, while avoiding an increase in size of the lid member. Moreover, the seal member is formed to surround the opening in the outer end of the insertion bore and hence, the passage defining member and the lid member can be reliably sealed from each other around the exhaust gas sampling pipe.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.